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A Level Biology Paper 1 > Key Points Document > Flashcards

Key Points Document Flashcards

1
Q

Cell wall function

A

Provides rigid shape

Stops osmotic lysis

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2
Q

Outline the roles of organelles in the production, transport and release of proteins from eukaryotic cells

A

DNA in nucleus codes for the protein
Ribosomes on the RER produce the protein
Mitochondria produce ATP needed for protein synthesis
Golgi apparatus modifies and packages protein into
vesicles
Vesicles transport the protein to the cell surface membrane where they fuse with it and undergo exocytosis to desired location

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3
Q

Compare and contrast DNA in prokaryotes and eukaryotes

A

Nucleotide structure identical
Nucleotides joined by phosphodiester bonds
Deoxyribose sugar
DNA in chloroplast and mitochondria similar to prokaryote

Eukaryotic longer
Eukaryotic contains introns
Eukaryotic is linear, Prokaryotic circular
Eukaryotic membrane bound, Prokaryotic free floating
Eukaryotic associated with histone

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4
Q

Differences between plant and prokaryotic DNA

A 
Plant associated with histones, Prokaryotic not
Plant linear, Prokaryotic circular
Plants have no plasmids, Prokaryotes do
Plants have introns, Prokaryotes do not
Plants longer
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5
Q

How is cholera different to epithelial cells

A

Cholera is prokaryotic, epithelial Eukaryotic
Cholera has no nuclear membrane and DNA free floating and circular
Cholera has no membrane bound organelles
Or SER/RER
Cholera only has small ribosomes
Cholera has a flagella, capsule, plasmid or cell wall

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6
Q

Advantage of TEM over SEM

A

Higher resolution
Higher magnification so more detail/internal details to be seen
Cross sections can be taken

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7
Q

Advantage of SEM over TEM

A

Can be 3D
Thin sections do not need to be prepared
Shows surface of specimen

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8
Q

Advantages vs disadvantages of TEM

A

Small objects can be seen
High resolution
Electrons wavelength is shorter than light

Cant look at living cells, must be dead
Must be a thin specimen
Must be in a vacuum
Risk of creating artefacts in preparation

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9
Q

Why isotonic

A

Prevents osmosis so organelle doesn’t burst of shrivel

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10
Q

Why ice cold

A

Reduce enzyme activity so organelles are not digested

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11
Q

Why add a buffer

A

Maintain a constant pH so proteins do not denature

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12
Q

How can cell fractionation and centrifugation be used to isolate mitochondria from a suspension of animal cells

A

Cell homogenisation to break open cells and release organelles
Filter to remove large debris like cell walls
Use isotonic solution to prevent osmotic damage to mitochondria
Keep ice cold to prevent damage to organelles by enzymes
Use a buffer to maintain pH so proteins don’t denature
Use differential centrifugation to separate nucleus in first pellet since densest
Re spin supernatant at a higher speed and the next pellet is mitochondria
Observe with microscope to check it is mitochondria

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13
Q

Why fluid mosaic

A

Fluid because molecules can move around within the membrane

Mosaic because made up of a variety of different molecules unevenly distributed

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14
Q

How is movement across cell membrane affected by membrane structure

A

Phospholipid bilayer allows lipid soluble substances to enter by simple diffusion
Stops polar, charged and water soluble molecules entering
Carrier proteins allow active transport
Channel and carrier proteins allow facilitated diffusion
Cholesterol affects permeability
Surface area determines how much diffusion
Number and type of channel proteins and carrier proteins determines how much is transported and what is transported

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15
Q

Non-specific defence mechanisms against pathogen

A 
Phagocytosis
Pathogen engulfed by phagocyte
Entering its cytoplasm in a vesicle
Lysosomes fuse
Releasing hydrolytic digestive enzymes
Lysozymes break down the pathogen
Waste ejected from cell via exocytosis
Becomes and APC
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16
Q

Cells that can stimulate an immune response

A

Abnormal body cells
Pathogens
Cells from other organisms like transplant
Cells infected by virus

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17
Q

How do vaccines cause production of antibodies

A

Vaccine contains antigens from pathogen
Macrophage presents the antigens on its cell
T helper cell with complementary receptor protein binds to antigen
Stimulating specific B cell with complementary antibody on its surface
B cell divides by mitosis in clonal selection
Producing more of the antibody
And memory B cells
B cells secrete large amounts of antibody

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18
Q

How does the humoral response lead to immunity

A

B cells specific to antigen undergo clonal selection by mitosis
B cells produce plasma cells and memory cells
Second infection produces antibodies quickly in large volumes

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19
Q

Role of antibodies in stimulating phagocytosis

A

Bind to antigen and act as markers for opsonisation

Clump pathogens together so easier to destroy

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20
Q

Active vs passive immunity

A

Active involves memory cells
Active involves production of antibody by plasma cells
Passive involves antibody introduced from external source
Active is long term because antibody produced in response to antigen
Passive is short term since antibody is broken down
Active can take longer to develop and passive is faster acting

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21
Q

Monoclonal antibody

A

Antibodies produced from a single clone of B cells

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22
Q

Why are monoclonal antibodies specific

A

Specific primary structure
Specific tertiary structure
So can only bind to one type of antigen

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23
Q

Structure of HIV

A

Human Immunodeficiency Virus

RNA is the genetic material
Reverse transcriptase contains genetic blueprint to rewrite human gene to manufacture viral particles
Protein capsid
Phospholipid envelope made from cell membrane of cell budded off
Attachment proteins allow it to bind to host cell

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24
Q

How does a person with HIV develop AIDS and die of secondary infections

A

High viral load leads to increased destruction of T helper cells
Less activation of B cells
Less production of antibodies
Less able to destroy other microorganisms or abnormal body cells

25
How do antibodies contribute to a positive ELISA
First antibody binds to complementary antigen Second antibody with enzyme attached is added Second antibody attaches to antigen Substrate added causing a colour change
26
Prophase
Nuclear membrane begins to break down Centrioles move to opposite poles of cell Chromatin supercoils and condenses into chromosomes
27
Metaphase
Spindle fibres form Spindle fibres attach to centromere of chromosomes Chromosomes align along the equator
28
Anaphase
Spindle fibres contract and shorten Centromere splits Sister chromatids are separated Chromatids pulled to opposite poles of cell
29
Telophase
Nuclear membrane begins to reform | Chromosomes unwind
30
Homologous pair
Two chromosomes carrying the same genes in the same loci
31
How to make a mitotic index accurate
Repeat count to ensure figures are correct Large number of fields of view so representative Only count cells half or more in view to standardise counting
32
How does meiosis result in haploid chromosome number and show genetic variation
Homologous chromosomes pair up Maternal and paternal chromosomes are arranged in any order Independant segregation Crossing over Equal lengths of non sister chromatids exchanged between chromosomes Producing recombinant alleles/new combinations Chromatids separated at meiosis ll
33
What is crossing over and how does it increases genetic diversity
Homologous pairs of chromosomes associate and for a bivalent Chiasmata forms Equal lengths of non sister chromatids exchanged Producing new combinations of alleles
34
Mitosis vs Meiosis
Mitosis is one division, meiosis is two Mitosis produces genetically identical daughter cells whereas meiosis is genetically different Two produced in mitosis whereas four in meiosis Diploid to diploid in mitosis, diploid to haploid in meiosis Crossing over only in meiosis Independant segregation only in meiosis
35
Exon
Base/nucleotide/triplet sequence coding for a polypeptide of amino acids
36
Transcription in eukaryotes
Hydrogen bonds between DNA bases are broken by DNA helicase Only one strand acts as a template Free RNA nucleotides attracted to complementary base pair Uracil with Adenine and Cytosine with Guanine RNA polymerase joins adjacent RNA nucleotides By phosphodiester bonds Pre-mRNA is spliced to form mRNA and introns removed
37
Describe translation
mRNA attaches to ribosome Moves along to find the start codon tRNA anticodons bind to complementary mRNA codons tRNA brings the specific amino acid Which are joined by peptide bonds with energy from ATP tRNA released after amino acid added to polypeptide Ribosome moves along the mRNA and forms the polypeptide until reaches the stop codon Ribosome can read two codons at once
38
Differences between mRNA and tRNA
``` mRNA has no hydrogen bonds but tRNA does mRNA linear tRNA clover leaf mRNA has no amino acid binding site tRNA does mRNA has more nucleotides tRNA are all similar length, mRNA varies mRNA has codons, tRNA has anticodons ```
39
Degenerate code meaning
More than one codon codes for an amino
40
Non overlapping meaning
A base from one triplet cannot be used in an adjacent triplet
41
How can a mutation in DNA base sequence lead to a non functional enzyme
Change in DNA base sequence Change in primary structure/amino acid sequence Change in hydrogen, ionic and disulphide bonding Change in tertiary structure Change in active site No longer complementary to substrate so cant form an ESC
42
Two reasons why not all mutations cause a change
Triplets code for the same amino acid | Occurs in non coding sequence/intron
43
Phylogenetic group
Grouped according to evolutionary links/history
44
Hierarchy
Groups within groups | No overlap between groups
45
Genetic diversity
Differences in DNA base sequence/alleles of a population
46
Why is index of biodiversity better
Some species may be present in high or low numbers | Also measures the number of individuals in each species
47
How can comparisons of biological molecules be used to find out if closely related
Genetic variation; compare DNA base sequence/compare mRNA base sequence/compare sequence of amino acids DNA hybridisation by separating strands of DNA; mix DNA strands of different species/heat required to separate strands indicates relationship Immunological evidence; Inject x1 protein into x2/obtain antibodies/add protein from x2/amount of precipitate indicates relationship
48
Why is it better to classify from base sequence of gene than amino acid sequence of a gene
There are more bases than amino acids and base sequence is longer Introns present in DNA but aren't expressed in amino acids Same amino acid can be coded for by different triplet due to degenerate DNA code
49
Describe the process that leads to a reduction in genetic diversity
Reduced number of different alleles/reduced gene pool Founder affect A few individuals from a population become isolated Genetic bottle necks Significant fall in size of population Selective breeding and artificial selection Using organisms with particular alleles/phenotypes
50
How can protein structure be used to investigate evolutionary relationship between species
Amino acid sequence Is coded for by DNA base sequence Closer amino acid sequence means closer relationship
51
Why does species diversity decrease when forests are cleared to make land available for agriculture
Decreased variety of plants and fewer species Fewer niches/habitats Decrease in variety of food/fewer food sources Machinery and pesticides cause harm to organisms that were present Pesticides kill species
52
Genetic bottle neck
Sudden decrease in population/many killed by an event like earthquake Reducing genetic variation
53
Ethical arguments for maintaining biodiversity
Prevents extinction | Save organisms for future generations
54
Economic arguments for maintaining biodiversity
``` Medical/pharmaceutical uses Commercial products like wool Tourism Agriculture Saving local forest communities ```
55
How can clearing forests lead to reduced diversity of insects
Lower diversity of plants so fewer plant species Fewer sources of food Fewer habitats/niches Pesticides and insecticides kill insects
56
How does courtship increase probability of successfully mating
``` Attracts mate of same species Attracts mate of opposite sex Indication of fertility/sexual maturity Stimulates release of gametes Form pair bond ```
57
Considerations for mark release recapture
No change in population size (no births, deaths, migration or emigration) Markings should not make animals more susceptible to predators Markings should not rub off or be lost Sufficient time for fully dispersing through rest of population
58
Measure wind speed, soil pH, temperature and light intensity
Anemometer pH probe Digital thermometer Lux meter

A Level Biology Paper 1 (16 decks)

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